The subject matter disclosed herein relates to a fieldbus system, and more specifically to a fieldbus system having a controller transmitting a plurality of high priority Receive Process Data Objects (RPDOs) and low priority RPDOs to a plurality of fieldbus devices.
A fieldbus is employed to monitor and control one or more pieces of production equipment such as, for example, sensors, actuators, electrical motors, or valves. A fieldbus is generally the equivalent of a local area network (LAN) type connection that requires only one communication point at a controller and allows for multiple pieces of production equipment to be connected concurrently. In one example, a transfer data protocol such as, for example, CANopen may be used to allow communication between the controller and the production equipment. Process data objects (PDOs) are used for broadcasting control and status information between the controller and the production equipment. Specifically, in order to communicate data from the controller to the production equipment, a Receive Process Data Object (RPDO) message is used.
The controller sends both high and low priority RPDOs according to a predefined schedule that is based on the specific CANopen configuration and production equipment specifications. Thus, the controller is typically configured with a unique RPDO transmission schedule to accommodate the RPDO transmission schedules of the production equipment. This means a firmware change is needed in the controller each time the specific CANopen configuration or the production equipment is modified. Changing the firmware in the controller each time the CANopen configuration or the production equipment is modified may become time consuming and may also be costly.